A recent study published on May 4, 2014 in Nature Medicine found that exposure of aged mice to young mouse blood can reverse age-related impairments in learning, memory and neuronal function. These findings suggest that in mice, circulating factors from young mouse blood could reverse the effects of aging on the brain. Aging changes the adult brain both structurally and functionally. These changes lead to a decline in cognitive function and an increased susceptibility to degenerative disorders. Previous studies have shown that blood-borne factors in aged mice can impair cognitive function in young mice. Whether there are also systemic factors in young blood that can reverse these age-related cognitive impairments is unclear.
As the human lifespan increases, the proportion of the population over 65 years of age has been increasing. From 2000 to 2010, the population in Connecticut aged 65 and over has increased by 8% (15% in the United States), while the population aged 85 years and over has increased by 32% (30% in the United States). This increase is particularly striking since the total population in Connecticut only increased by 5% (10% in the United States) from the year 2000 to 2010. With this increase in the proportion of elderly people, a greater fraction of the population is suffering from age-related cognitive impairments.
This recent study found that repeated injection of blood from 3-month-old mice (young) into 18-month-old mice (aged; typical lifespan ~2 years) can improve their performance in learning and memory tasks. Heating the blood, which alters the structure of its proteins, before injecting it into older mice abolishes these effects, suggesting a circulating heat-sensitive factor mediates these positive effects. The results showed that exposure of an aged animal to young blood can counteract and reverse the effects of brain aging at the molecular, structural, functional, and cognitive level. Further studies are needed to determine if factors in human blood have similar capabilities.